Electric micromotor

Abstract

A miniature electric motor ( 1 ) with an outer diameter (D A ) that is smaller than or equal to 6 mm, has a hollow cylindrical stator ( 2 ) with stator coils ( 8 ) and a magnetic rotor ( 4 ) rotatably arranged around a rotational axis ( 16 ) in the stator ( 2 ) by means of a rotor shaft ( 10 ). The stator coils ( 8 ) can be energized in order to generate a magnetic rotational field in dependence upon the rotational position of the magnetic rotor ( 4 ). A sensor chip ( 20 ) having at least one magnetic field sensor ( 22 ) is arranged in such a manner in an area axially adjacent to a front face of the magnetic rotor ( 4 ) located within a plane that is vertical to the rotational axis ( 16 ) that the magnetic field sensor ( 22 ) is impinged in such a way by the magnetic field that the rotational position of the rotor can be evaluated.

The invention claimed is: 
     
       1. A miniature electric motor ( 1 ) with an outer diameter (D A ) that is smaller than or equal to 6 mm, comprising,
 a hollow cylindrical stator ( 2 ) with stator coils ( 8 ), 
 a magnetic rotor ( 4 ) arranged so as to rotate around a rotational axis ( 16 ) in the stator ( 2 ) by means of a rotor shaft ( 10 ), wherein the stator coils ( 8 ) can be energized in order to generate a magnetic rotational field in dependence upon the rotational position of the magnetic rotor ( 4 ), 
 a sensor chip ( 20 ) arranged concentrically with respect to the rotational axis ( 16 ), having at least four magnetic field sensors ( 22 ), and arranged in an area axially adjacent to a front face of the magnetic rotor ( 4 ) located within a plane that is vertical to the rotational axis ( 16 ) for the purpose of detecting the rotational position of the magnetic rotor ( 4 ), wherein the sensor chip ( 20 ) is spaced from an adjacent front face of the magnetic rotor ( 4 ) via an axial gap (A) in such a way that the magnetic field of the magnetic rotor ( 4 ) passes through several components until it reaches the area of the sensor chip ( 20 ) and that the magnetic field sensors ( 22 ) are impinged in such a way by the magnetic field of the magnetic rotor ( 4 ) that the magnetic field can be evaluated in order to determine the rotational position of the rotor. 
 
     
     
       2. The electric miniature motor of  claim 1  wherein the magnetic field sensors are integrated magnetic field sensors ( 22 ), which are arranged in an area that covers an axial projection of the magnetic rotor ( 4 ) and in a specific peripheral distribution over a reference circle ( 24 ) around the rotational axis ( 16 ), wherein the reference circle ( 24 ) has a diameter (D T ), which is located in the area between the diameter (D W ) of the rotor shaft ( 10 ) and the outer diameter (D A ) of the magnetic rotor ( 4 ). 
     
     
       3. The electric miniature motor of  claim 2  wherein the axial gap (A) corresponds to a maximum of 1 to 1.5 times the diameter (D T ) of the reference circle ( 24 ) of the magnetic field sensors ( 22 ). 
     
     
       4. The electric miniature motor of  claim 1  wherein the sensor chip ( 20 ) has exactly four magnetic field sensors ( 22 ), which are evenly distributed over the reference circle ( 24 ) and are mutually offset by 90° respectively, with respect to each other. 
     
     
       5. The electric miniature motor of  claim 1  wherein the sensor chip ( 20 ) is configured as a single chip encoder, which has a signal evaluation circuit, in addition to the magnetic field sensors ( 22 ), and delivers an absolute or incremental rotational position signal for an external electronic control system. 
     
     
       6. The electric miniature motor of  claim 1  wherein the sensor chip ( 20 ), is electrically connected via a flexible conductor foil ( 26 ). 
     
     
       7. The electric miniature motor of  claim 1  wherein the sensor chip ( 20 ) is mechanically exactly positioned relative to the stator ( 2 ) and the magnetic rotor ( 4 ). 
     
     
       8. The electric miniature motor of  claim 7  wherein the stator ( 2 ) is connected on one side to a flange-like receiver part ( 28 ), wherein the receiving part ( 28 ) has a wall ( 30 ), which is vertical with respect to the rotational axis ( 16 ), and has a receiving opening ( 32 ) for play-free positioned accommodation of the sensor chip ( 20 ). 
     
     
       9. The electric miniature motor of  claim 6  wherein the flexible conductor foil ( 26 ) has a chip carrier section ( 34 ) connected to the sensor chip ( 20 ) and a stator section ( 36 ) electrically connected to the stator coils ( 8 ), wherein the chip carrier section ( 34 ) and the stator section ( 36 ) are arranged in two parallel and offset planes and are mutually connected via a folded-over connecting section ( 38 ). 
     
     
       10. The electric miniature motor of  claim 9  wherein the stator section ( 36 ) of the conductor foil ( 26 ) is mounted on a bearing shield ( 40 ) of the stator ( 2 ), wherein the winding taps ( 44 ) of the stator coils ( 8 ) are soldered. 
     
     
       11. The electric miniature motor of  claim 6  wherein the flexible conductor foil ( 26 ) has a terminal section ( 52 ) for external electrical motor connection. 
     
     
       12. The electric miniature motor of  claim 1  wherein the magnetic rotor ( 4 ) is arranged inside the stator ( 2 ) with an offset in the axial direction relative to the stator coils ( 8 ) and off-center in the direction toward the sensor chip ( 20 ). 
     
     
       13. A miniature electric motor ( 1 ) with an outer diameter (DA) that is smaller than/equal to 6 mm, comprising a hollow cylindrical stator ( 2 ) with stator coils ( 8 ), a magnetic rotor ( 4 ) arranged so as to rotate around a rotational axis ( 16 ) in the stator ( 2 ) by means of a rotor shaft ( 10 ), wherein the stator coils ( 8 ) can be energized in order to generate a magnetic rotational field in dependence upon the rotational position of the magnetic rotor ( 4 ),
 a sensor chip ( 20 ), having at least one magnetic field sensor ( 22 ), is arranged in an area axially adjacent to a front face of the magnetic rotor ( 4 ) located within a plane that is vertical to the rotational axis ( 16 ) for the purpose of detecting the rotational position of the magnetic rotor ( 4 ), the magnetic field sensor ( 22 ) is impinged in such a way by the magnetic field of the magnetic rotor ( 4 ) that the magnetic field can be evaluated in order to determine the rotational position of the rotor, wherein the sensor chip ( 20 ), which is preferably configured according to the flip chip technology, is electrically connected via a flexible conductor foil ( 26 ), wherein the flexible conductor foil ( 26 ) has a chip carrier section ( 34 ) connected to the sensor chip ( 20 ) and a stator section ( 36 ) electrically connected to the stator coils ( 8 ), wherein the chip carrier section ( 34 ) and the stator section ( 36 ) are arranged in two parallel and offset planes and are mutually connected via a folded-over connecting section ( 38 ). 
 
     
     
       14. The electric miniature motor of  claim 13  wherein the sensor chip ( 20 ) having four magnetic field sensors ( 22 ), which are evenly distributed over the reference circle ( 24 ) and are mutually offset by 90° respectively, with respect to each other. 
     
     
       15. The electric miniature motor of  claim 13  wherein the stator section ( 36 ) of the conductor foil ( 26 ) is mounted on a bearing shield ( 40 ) of the stator ( 2 ), wherein the winding taps ( 44 ) of the stator coils ( 8 ) are soldered. 
     
     
       16. The electric miniature motor of  claim 13  wherein the flexible conductor foil ( 26 ) has a terminal section ( 52 ) for external electrical motor connection. 
     
     
       17. The electric miniature motor of  claim 13  wherein the sensor chip ( 20 ) is configured as a single chip encoder, which has a signal evaluation circuit, in addition to the magnetic field sensors ( 22 ), and delivers an absolute or incremental rotational position signal for an external electronic control system.